Intermetallic ruthenium tin-catalyst for use in aldehyde synthesis

ABSTRACT

The present invention relates to a composition which can be used as reduction catalyst. 
     This composition is characterized in that it comprises a support whose constituent material comprises at least one oxide chosen from oxides which are inert or capable of being made inert relative to the reaction mixture and a phase at least partially covering the said support, of which at least part comprises an intermetallic ruthenium-tin compound of composition Ru 3  Sn 7 . The invention also describes the use of the reduction catalyst and its application to organic synthesis.

This application is a continued Prosecute Application of applicationSer. No. 08/716,399, filed: Jul. 31, 1997, which is a 371 ofinternational application number PCT/FR96/00101, filed Jan. 22, 1996.

The present invention relates to a process for preparing aldehydes andderivatives thereof by vapour-phase reduction in the presence ofhydrogen, acids, esters or carboxylic anhydrides.

It relates more particularly to a process for the synthesis of aldehydesby vapour-phase reduction of acids, esters or derivatives thereof in thepresence of a bimetallic catalyst of the ruthenium/tin type. It alsorelates to a catalyst and to its use for the selective reduction ofcarboxylic derivatives to aldehydes.

The present process relates more particularly, as substrate, tocarboxylic compounds which carry halogen, and especially fluorine, andare capable of undergoing hydrogenolysis in the course of reduction.

It is known in the prior art to prepare saturated aliphatic or aromaticaldehydes by reduction of the corresponding esters or acids using acatalyst chosen from the oxides of cerium, zirconium, uranium,praseodymium and yttrium at a temperature of between 350 and 450° C.(U.S. Pat. No. 4,328,373).

Owing to the temperature conditions required for their implementation,these processes do not permit preparation of aldehydes from thermallyunstable acids.

The patent application published under the U.S. Pat. No. 2,682,949described a technique using alloys of ruthenium and tin which permits asignificant improvement.

Catalysts of the Ru/Sn/B type had already been described in theliterature [J. Cat., 121, 165-173 (1990)], as had their use for theliquid-phase reduction of unsaturated fatty acids to unsaturated fattyalcohols [J. Cat., 121, 174-182 (1990)].

Certain problems remained unresolved. For a certain number ofsubstrates, giving rise to secondary reactions, the choice of thesupport and of the manner in which the surface catalytic layer wasformed was found to be critical. The problem is particularly acute inthe case of the reduction of certain halogenated derivatives, whoselysis by hydrogen leads to particularly aggressive acids such as, forexample, hydrofluoric acid.

These acids are capable of destroying certain supports and interferewith the desired reaction. A further risk lies in a catalysis of thereduction of the aldehyde to alcohol.

For this reason, one of the aims of the present invention is to providea composition which can be used as catalyst and permits improvedresistance to products of any secondary reaction(s).

Another aim of the present invention is to provide a composition of theabove type which avoids the secondary reactions or reduces theirrelative importance.

These and other aims which will become evident below are achieved by acomposition which can be used as reduction catalyst and which comprisesa support whose constituent material comprises at least one oxide chosenfrom oxides which are inert or capable of being made inert relative tothe reaction mixture and a metallic phase at least partially coveringthe said support, of which at least part comprises an intermetallicruthenium-tin compound at least some of which is in the form of thedefined compound Ru₃ Sn₇.

The phase containing the ruthenium and the tin advantageously has anSn/Ru atomic ratio which is at least equal to 2/3, advantageously to3/2, preferably to 7/3. Moreover, it is preferable for the Sn/Ru atomicratio to be at most equal to 3, advantageously to 5/2.

The said phase covering at least part of the said support advantageouslycontains at least 50%, more advantageously 80%, preferably at least 90%,of the said intermetallic phase.

Finally, it is desirable for at least 90%, advantageously at least 95%,preferably 98%, of the ruthenium present on the support to be in theform of the said phase covering the said support.

The invention is more particularly suitable for the preparation ofaldehydes of general formula: ##STR1## in which R represents a hydrogenatom or an optionally substituted hydrocarbon radical containing 1 to 40carbon atoms which can be a linear or branched, saturated or unsaturatedacyclic aliphatic radical or a monocyclic or polycyclic, saturated,unsaturated or aromatic carbocyclic or heterocyclic radical, byreduction of esters, anhydrides or acids of formula: ##STR2## in which:R is defined as above,

R' represents:

a group R as defined above,

a group ##STR3## in which R" has the meaning given for R, it beingpossible for the two groups R and R" to be linked to one another to forma saturated or unsaturated ring having 5 to 7 atoms and including theanhydride functional group, and

it being possible for the two groups R and R" together to form, by wayof two vicinal atoms, a bridge of an ortho-condensed bicyclic system.

The carboxylic acids or derivatives preferably employed correspond tothe formula (II) in which R represents an optionally substitutedhydrocarbon radical containing 1 to 20 carbon atoms.

The invention is quite suitable for the preparation of aldehydes fromhalogenated aliphatic carboxylic acids, such as fluoral.

The invention is highly suited to the synthesis of aldehydes fromaromatic carboxylic acids and halobenzoic acids, preferablyfluorobenzoic acids.

In the following description of the present invention the term aromaticcompound is understood as denoting the traditional idea of aromaticityas defined in the literature, in particular by Jerry MARCH--AdvancedOrganic Chemistry, 3rd edition, John Wiley and Sons, 1985, p. 37 et seq.

The term benzoic acid refers to any benzenic compound carrying at leastone COOH functional group.

As indicated above, it is also possible to employ the carboxylic acid asdefined above in the form of its ester. In this case, in the formula(II), R' preferably represents an optionally substituted aliphaticradical containing 1 to 10 carbon atoms. More preferably, R' representsa linear or branched alkyl radical having 1 to 6 carbon atoms.

Examples of preferred radicals R' which may be mentioned are theradicals methyl, ethyl or hexyl.

The invention is particularly well suited to the synthesis of aldehydeswhose formulae include one or more halogens, especially when at leastsome of these halogens are fluorines.

The invention is aimed particularly at aldehydes obtained fromperhalocarboxylic acids or acids which are equivalent to these in termsof their reactivity. Thus equivalents of perhalocarboxylic acids areacids whose vicinal carbon, or rather the two carbons vicinal to thecarboxyl functional group, are perhalogenated.

Thus the invention is particularly well suited to the synthesis ofaldehydes where the vicinal carbon, or rather the two vicinal carbons,are perfluorinated.

In accordance with the present invention it is possible to employ acarboxylic acid in the form of its anhydrides and esters.

Examples of carboxylic anhydrides which may be mentioned moreparticularly are the homoanhydrides, which may be internal (cyclicanhydrides) or otherwise, and heteroanhydrides (or mixed anhydrides).

The preferred compounds are bicyclic and are formed from a benzene ring.

The process of the invention is carried out in the gaseous phase. Thereaction is advantageously conducted at a temperature of between 100° C.and 500° C., more preferably between 200 and 400° C. It is understoodthat the temperature is adapted by the person skilled in the art independence on the starting acid and on the desired reaction rate.

As has been mentioned above, it is highly desirable for the phasecontaining the ruthenium and the tin to have an Sn/Ru atomic ratio whichis at least equal to 2/3, advantageously equal to 3/2, preferably equalto 7/3. Moreover, it is preferable for the Sn/Ru atomic ratio to be atmost equal to 3, advantageously to 5/2.

In the course of the study which led to the present invention, in orderto obtain such values it was shown how important it was to carry outforced reduction at relatively high temperature so as to attain theabove proportions of tin. Indeed, in the above proportions the tincontents take account only of metallic tin.

The documents of the prior art describe only mild reduction techniqueswhich appear to be entirely inadequate for reducing tin in order toapproach the optimum zone corresponding to the intermetallic compoundRu₃ Sn₇.

In effect it has been shown that, in order to obtain optimum effects,the reduction described in the prior documents was inadequate to theextent that the intermetallic Ru₃ Sn₇ compound, if it existed, was inproportions which were too low for it to play its part as a selectivecatalyst.

It is possible to obtain an intermetallic phase according to the presentinvention by impregnating the support with salts or oxides andsubjecting it to reduction by a stream (for example under at least 2×10⁵Pa) of hydrogen (or of a gas which is a source of hydrogen under theconditions of the process, such as propylene and, for instance,ethylene) at a temperature of at least 400° C., preferably at least 450°C. The impregnating substance includes a proportion of tin which is atleast equal to that of Ru₃ Sn₇ and is preferably significantly greater.

The lower the temperatures, the longer the treatment must last. At atemperature of 400° C. one day is a minimum, whereas this minimum isonly about 5 hours at 450° C. In a first stage, it appears that theruthenium catalyses the reduction of the tin and that, under theseconditions, the excess tin is at least partly eliminated and that theintermetallic phase on the support comes close to the Ru₃ Su,composition. The longer the duration of this stage, the closer one comesto the optimum composition of the catalyst, with the proviso that anexcess of tin is available.

A practical method of implementing the present invention consists inintroducing a desired quantity of catalyst into a reactor. Thetemperature of the reactor is then raised under a stream of hydrogen toa predetermined value, enabling activation of the catalyst, and thenbrought to the reaction temperature. The acid is subsequently injectedat the desired rate and the aldehyde formed is recovered.

The acid is preferably injected directly in gaseous form after havingbeen vaporized by heating.

However, it can also be injected in solution in a solvent which is inertfor the reaction. As inert solvents particular mention may be made ofaliphatic hydrocarbons (for example hexane), alicyclic hydrocarbons (forexample cyclohexane), aromatic hydrocarbons (for example toluene) orethers (for example dimethoxyethane). Under the effect of thetemperature, the acid thus injected is vaporized. The hydrogen can beinjected at atmospheric pressure or under a slight superatmosphericpressure which is compatible with the vapour phase (a partial pressureof a few bars, for example from 0.5 to 10 bar, the bar here being takento represent 10⁵ Pa). The hydrogen can also be diluted in a gas which isinert under the operating conditions, such as nitrogen or helium.

Advantageously for 1 ml of catalyst, the hydrogen is injected at a rateof between 0.1 and 10 liters per hour and the acid at a liquid flow rateof not more than 10 ml/h and preferably between 0.5 and 5 ml/h.

At the end of the reaction, the aldehyde is recovered by any suitablemeans, such as distillation or crystallization. In certain cases,especially in the case of fluoral, the aldehyde can be obtained in ahydrated form.

The content of any extraneous element(s) such as boron is generally lessthan 1% and preferably less than 0.1% in molar terms.

Generally, the two metals in the form of salts are dissolved in water,optionally in the presence of the support, and impregnation is allowedto take place over a period of approximately 15 hours. The support isthen dried (for example under vacuum) before being used.

One of the processes for its preparation consists, for example, inintroducing a support into a solution which is prepared by dissolving atleast one appropriate compound of the chosen elements; the deposition ofthe active elements on the support is carried out by distilling thesolvent, preferably water, which can be eliminated by evaporation undera reduced pressure which is chosen, preferably, between 5 and 20 mm ofmercury. The catalyst mass thus obtained is subjected to reduction bymeans of a stream of hydrogen.

According to another, conventional mode of preparation, the depositionof the compound or compounds providing the metallic elements on thesupport is carried out by means of compounds which have beenprecipitated beforehand in a manner known per se, and by subjecting thecatalyst mass thus obtained to reduction by means of hydrogen.

The deposition on the support of two or more metallic elements may ofcourse be carried out in succession, but preferably simultaneously.

The deposition of the precursors of the intermetallic phase can becarried out by repeating one of the abovementioned processes. Thisrepetition can be carried out either for repeat impregnations or forrepeat cycles of impregnation-reduction.

The nature of the compounds providing the metallic elements which areused for the preparation of the catalysts of the invention is notcritical provided that there is no risk of modification of thetin/ruthenium ratio before the great majority (at least 3/4,advantageously 9/10, preferably 95%) of the ruthenium has entered into ametallic phase with the tin.

It is possible to employ the metals themselves, such as ruthenium andtin.

As examples of compounds which can be employed for the preparation ofthe catalysts of the invention mention may be made, by way of rutheniumcompounds, of ruthenium(III) chloride, ruthenium(IV) chloride, rutheniumpentafluoride, ruthenium(II) oxide, ruthenium(IV) oxide, ammoniumruthenium oxychloride Ru₂ (OH)₂ Cl₄.7NH₃.5H₂ O, and ruthenium acetate,and, by way of tin compounds, of tin oxides, chlorides, nitrates,carboxylates and alcoholates or organometallic compounds in which thetin is linked to a hydrogen atom and/or to alkyl radicals havingpreferably 1 to 4 carbon atoms. The preferred salts are as follows:ruthenium compounds such as ruthenium(III) chloride, and tin compoundssuch as tin(II) chloride, tin(IV) chloride, tin(II) acetate, tin(II)octoate and tin ethylhexanoate.

It would not be departing from the scope of the present invention tomanufacture, in accordance with the process of the invention, thealdehydes in the form of their derivatives, such as their acetals, theirhemiacetals or their bisulphite combinations, by reacting the aldehydeand the reactant [alcohol in the case of the (hemi)acetals] which isintroduced either conjointly with the acid, when the reactant isvolatile, or at the end of reaction. As examples of alcohols which canconventionally be used mention may be made of methanol or ethanol.

One of the most important aspects of the invention lies in the choice ofsupport.

The support must be chosen in order to maximize the resistance to theindustrial conditions, and in particular the resistance to mechanical orquasi mechanical abrasion, especially the resistance to attrition.

The support must be chosen so as to avoid substantial head losses whilepermitting good contact between the gases and the catalyst.

The support must be chosen from oxides which are inert (i.e. have a goodchemical resistance to) or are capable of being made inert relative tothe reaction mixture. The problem is particularly acute in the casewhere the chosen substrate comprises carboxylic acids having halogenatoms, especially fluorine atoms.

In this case it is preferable for the support to show significantresistance to wet halohydric acids, and especially to wet gaseoushydrofluoric acid (the reduction to aldehyde of an acid produces water).

The said support is advantageously one which is capable of being madeinert by the action of the gaseous hydrofluoric acid without losing itsexternal geometry and its mechanical strength.

The various silicas are not resistant to the action of hydrofluoricacid.

It should be noted that supports of the charcoal type should be avoidedin particular, since they promote secondary reactions and give rise tointense coking of the substrates.

Metal oxides which can be chosen are those such as the oxides ofaluminium or of zirconium. Mixed oxides are also suitable, moreespecially those containing at least 1/4, advantageously 1/3, preferably2/5 by mass of aluminium expressed as Al₂ O₃.

The said support advantageously has a silicon content which, expressedas SiO₂, is at most equal to 2/3 of the total weight, advantageously atmost equal to 1/4.

The ceramics obtained by firing, at at least approximately 1000° C.,clays containing as principal elements the oxides of aluminium and ofsilicon have been tested and found to give particularly advantageousresults. As silicoaluminous clay giving good results mention may be madeof Provins clays, especially those sold by Denain Anzin Mineraux underthe trade name chamotte 40/42.

The said support advantageously has a particle size such that its d₂₀ isat least equal to 0.1 millimeter, advantageously to 0.5 millimeter,preferably to one millimeter.

A good compromise consists in choosing beads of low porosities of from 1mm to 1 cm, giving good results.

The specific surface area of the support is advantageously low, lessthan 10 m² per gram, preferably at most equal to 1 m² per gram.

The mass ratio between the support and the surface phase is between 1%and 30%, advantageously from 1 to 15%, preferably from 2 to 10%.

A further aim of the present invention is to provide a process whichmakes it possible to prepare the composition according to the presentinvention.

Another aim of the present invention is to provide a process of theabove type which makes it possible to obtain a covering phase which isas close as possible to the intermetallic ruthenium-tin compound ofcomposition Ru₃ Sn₇.

These aims and others which will become evident from what follows areachieved by means of a process comprising the following steps:

a) coating of the support by means of a solution or a suspension ofstanniferous and rutheniferous species, the Sn/Ru atomic ratio being atleast equal to 2.3, advantageously to 3, preferably to 4;

b) treatment at a temperature at least equal to 400°, advantageously to450° C., under a partial pressure of hydrogen which is at least equal to1/2×10⁵ Pa, advantageously between 1 and 10 bar, preferably between oneand two bar, for a period of at least approximately five hours,preferably at least 10 hours.

It is desirable for the choice of stanniferous and rutheniferous speciesto be made such that it minimizes volatilization during the reductionstage.

The following, non-limiting examples illustrate the invention:

CATALYST I Example 1 Preparation of a Batch of 9 Liters of 3.5%

Ru/ex-clay bead catalyst with an Sn/Ru ratio of 2.3

Preparation of the tin hydroxide suspension

Tin hydroxide is obtained by neutralizing SnCl₄.5H₂ O with aqueousammonia. 5 kg of SnCl₄.5H₂ O are dissolved in 3.1 liters of water.

13.45 liters of 5 M ammonia solution are then prepared by diluting 5liters of 28% aqueous ammonia.

Immediately before neutralizing the tin salt solution with aqueousammonia, this solution is diluted with 8.6 liters of water in order togive a tin salt concentration of 1.25 M.

Permanent and continuous precipitation is carried out in a one-literreactor fitted with a stirrer, a temperature control means, a continuouspH regulator, a level regulator and two feed pumps.

Downstream of this precipitation reactor there is a "reservoir" reactorwith a capacity of 10 liters for storage.

The initial charge is 1 liter of purified water.

The tin chloride solution is fed in at a constant flow rate of 2.5 1/h.The feeding of the ammonia solution depends on the pH regime imposed andon the deviation from this regime. The chosen pH of precipitation is 5.The stirrer is set at 700 rpm and the temperature is regulated at 30° C.

Once the conditions relating to level have been attained, the suspensionis drawn by suction out of the reactor.

Only after 5 passes is the reactor considered to be in a permanentregime, and only after this time is the gel obtained collected in thereservoir reactor.

Filtration is carried out through a Buchner funnel in order to evacuatethe mother liquors. The gel is subsequently repulped in 20 liters ofpurified water and the mixture is stirred for 6 hours. The suspension issubjected to decantation for 12 hours, and then filtered again in orderto separate the gel from the washing liquors.

The tin hydroxide gel thus obtained has a water content which variesdepending on the filtration efficiency and is measured by way of a losson ignition at 1000° C. between 55 and 70%.

Preparation of the active-phase precursor

The water content of the hydroxide gel, measured by the loss on ignitionat 1000° C., is 57% in this example.

By mixing the tin hydroxide gel and the hydrated salt of Ru(III)chloride, 4414 g of precursor are prepared containing 1361 g ofanhydrous SnO₂ and 397 g of Ru (in the form of 957 g of RuCl₃.xH₂ Ocontaining 43% Ru).

The following description of the preparation of the precursor is relatedto 1000 g of tin hydroxide gel containing 57% of water.

2.9 mol of RuCl₃.xH₂ O containing 43% of Ru (or 293.1 g of Ru) are addedto 1000 g of hydroxide gel containing 57% of water, i.e. 6.66 mol ofSnO₂.

For rapid mixing of the hydroxide and the salt (approximately 1 hour),260 g of water are added to the mixture, bringing the hydroxide gel to awater content of 65%; the paste thus obtained is highly fluid.

Therefore, 79 g of Degussa OX-50 silica are added as thickener so as toobtain the appropriate viscosity for coating.

2548 g of active-phase precursor are prepared in this way.

A variant consists in mixing the tin hydroxide gel and the Ru salt bymechanical stirring for a long period (24 h) without additionally addingeither water or silica.

Coating of the active-phase precursor on the T375 bead support

The 9 liters of T375 beads (11.25 kg) are placed in a film-coatingapparatus whose volume, the angle of the axis of rotation and the speedof rotation are chosen so as to avoid the loss of beads by expulsionfrom the film-coater and to obtain a vacant central area in the bed ofrotating beads.

The active-phase precursor prepared above is then poured gradually intothe rotating film-coater.

The coating of the beads by the active-phase precursor is perfectlyhomogeneous.

The addition of precursor is stopped when the beads are seen to have ashiny, slightly wet appearance.

Degussa OX-50 silica is then poured into the bed of rotating beads.

Rotation is then maintained for approximately 30 minutes in order tocomplete the coating of the layer of the precursor with silica.

The catalyst thus obtained is oven-dried under a vacuum of 540 mm Hg at80° C.

The height of the catalyst bed in the boat is limited to 2 cm.

Drying lasts between 5 hours and 16 hours.

After drying, the catalyst is replaced in the film-coater in order tocarry out the second coating of precursor.

The desired percentage of Ru is attained after 6 active-phase precursorcoating operations.

The series of coating operations of active-phase precursor and silicafor the preparation of the catalyst I is set out in the table in annexI.

The catalyst is ready for loading into the catalytic reactor where itwill be activated by reduction under hydrogen.

CATALYST II Example 2 Preparation of a Batch of 9 Liters of 3.1%

Ru/ex-clay bead catalyst with an Sn/Ru ratio of 3

The above preparation is reproduced with an Sn/Ru ratio of 3.

The preparation of the tin hydroxide gel follows the same procedure.

In this case the tin hydroxide gel has a water content after filtration,measured by its loss on ignition at 1000° C., of 65%.

The mixture of this hydroxide gel with the Ru salt at an Sn/Ru ratio of3 gives a paste which is too fluid to be applied as a coating to thebeads.

Drying under vacuum at 120° C. of the tin hydroxide makes it possible toreduce the residual water content to 57% (loss on ignition at 1000° C.).

The mixture of this tin hydroxide gel containing 57% of water with theRu(III) chloride salt in accordance with the above-described procedure(stirring for 24 hours) gives an active-phase precursor with an Sn/Ruratio of 3 which is suitable for carrying out coating.

A slightly greater fluidity of the precursor relative to the previouspreparation, and the use of a smaller quantity of silica for coating andstabilizing the successive layers of precursors ((149 g instead of 414g), make it necessary to carry out a total of 8 coating operations inorder to attain the desired percentage of Ru.

The totality of coating operations for the preparation of the catalystII is set out in the table in annex II.

The alumina beads were treated in 2 batches, as described above.

Example 3 Example of the Preparation of Fluoral Hydrate CF₃ CH(OH)₂ bySelective Reduction of Trifluoroacetic Acid CF₃ COH (TFA) by HydrogenGas in the Presence of a Catalyst whose Active Phase, Ru₃ Sn₇, isDeposited on Alumina Beads

28 g of catalyst are charged to a stainless-steel reactor (316 l) with alength of 30 cm. Following activation of the catalyst at elevatedtemperature in a stream of hydrogen, the catalyst bed is fed, under aconstant stream of hydrogen, with trifluoroacetic acid at a temperatureof between 250 and 400° C., the H₂ /TFA molar ratio being between 1.5and 4.

The crude reaction mixture is collected in a cold trap and then,following customary treatment, is analysed by gas chromatography:

selectivity for fluoral hydrate: 73%

conversion of the TFA: 75%

Similar tests using support phases of different types of alumina givesimilar results.

    __________________________________________________________________________    CATALYST I: Preparation of a batch of 9 liters of 3.5% Ru/T375 ex-clay        bead catalyst with an                                                         Sn/Ru ratio of 2.3                                                                     % of SnO.sub.2                                                                     g of                                                                             % Ru in           % Ru % Ru g of                             Weight of                                                                              in the                                                                             SnO.sub.2                                                                        the g of Ru                                                                           Total Ru  relative                                                                           relative to                                                                        Degussa 50                       active   active                                                                             intro-                                                                           active                                                                            intro-                                                                            intro-                                                                             %    to pre-                                                                            recovered                                                                          SiO.sub.2                        phase (g)                                                                              phase                                                                              duced                                                                            phase                                                                             duced                                                                             duced (g)                                                                          Ru/beads                                                                           cursor                                                                             mass introduced                       __________________________________________________________________________    1st 639  30   190                                                                              8.7 56   56  0.5            141                              coating                                                                       2nd 975  30   290                                                                              8.7 85  140  1.2            219                              coating                                                                       3rd 584  30   174                                                                              8.7 51  191  1.7             17                              coating                                                                       4th 477  30   145                                                                              8.4 40  231  2.1             15                              coating                                                                       5th 737  32   234                                                                              9.3 69  300  2.7             16                              coating                                                                       6th 1,001                                                                              33   328                                                                              9.6 96  396  3.5  16.4 2.8   6                               coating                                      414                              __________________________________________________________________________    Charge of T 375 clay beads (g)                                                              11,250                                                          Charge of Degussa silica (g)                                                                  414                                                           Charge of RuCl.sub.3.xH.sub.2 O (g)                                                           957                                                           Charge of SnO.sub.2 (g)                                                                      1,361                                                          TOTAL (g)     13,982                                                          Total mass recovered after final drying =                                                       14,080 g                                                    Total dried mass of active-phase precursor                                                       2,416 g                                                

    __________________________________________________________________________    CATALYST II: Preparation of a batch of 9 liters of 3.1% Ru/T375 ex-clay       bead catalyst with an                                                         Sn/Ru ratio of 3                                                                       % of SnO.sub.2                                                                     g of                                                                             % Ru in           % Ru % Ru g of                             Weight of                                                                              in the                                                                             SnO.sub.2                                                                        the g of Ru                                                                           Total Ru  relative                                                                           relative to                                                                        Degussa 50                       active   active                                                                             intro-                                                                           active                                                                            intro-                                                                            intro-                                                                             %    to pre-                                                                            recovered                                                                          SiO.sub.2                        phase (g)                                                                              phase                                                                              duced                                                                            phase                                                                             duced                                                                             duced (g)                                                                          Ru/beads                                                                           cursor                                                                             mass introduced                       __________________________________________________________________________    1st 545  30   162                                                                              6.6 36   36  0.3             7                               coating                                                                       2nd 580  30   166                                                                              6.6 37   73  0.6            28                               coating                                                                       3rd 620  30   184                                                                              6.5 41  114  1.0            65                               coating                                                                       4th 650  37   241                                                                              8.2 53  167  1.4            13                               coating                                                                       5th 830  36   301                                                                              8.1 67  234  2.0            10                               coating                                                                       6th 575  33   190                                                                              7.3 42  276  2.4             8                               coating                                                                       7th 745  33   244                                                                              7.3 54  330  2.8                                             coating                                                                       8th 575  33   190                                                                              7.3 42  372  3.1  13.2 2.6  18                               coating                                      149                              __________________________________________________________________________    Charge of T 375 clay beads (g)                                                              11,750                                                          Charge of Degussa silica (g)                                                                  149                                                           Charge of RuCl.sub.3.xH.sub.2 O (g)                                                           899                                                           Charge of SnO.sub.2 (g)                                                                      1,677                                                          TOTAL (g)     14,475                                                          Total mass recovered after final drying (g)                                                     14,715                                                      Total dried mass of active-phase precursor                                                       2,816                                                  

What is claimed is:
 1. A composition of matter usable as a catalyst in areaction mixture comprising:a support comprising at least one oxidechosen from oxides which are inert or capable of being made inertrelative to the reaction mixture; and a metallic phase at leastpartially covering said support, of which at least part comprises anintermetallic ruthenium-tin compound at least some of which is in theform of thc defined compound Ru₃ Sn₇, said metallic phase having a Sn/Ruatomic ratio of at least equal to 2/3 and at most equal to
 3. 2. Acomposition according to claim 1, wherein said support is made inert bythe action of gaseous hydrofluoric acid without losing its externalgeometry.
 3. A composition according to claim 1, wherein said metallicphase contains at least 50%, of Ru₃ Sn₇ compound.
 4. A compositionaccording to claim 3, wherein said metallic phase contains at least 90%,of Ru₃ Sn₇ compound.
 5. A composition according to claim 1, wherein themass ratio between said support and said metallic phase is between 0.5%and 10%.
 6. A composition according to claim 1, wherein the mass ratiobetween said support and said metallic phase is between 1% and 5%.
 7. Acomposition according to claim 1, wherein said support is an oxidecontaining aluminum.
 8. A composition according to claim 1, wherein saidsupport has a silicon content which, expressed as SiO₂, is at most equalto 2/3 of the total weight of the composition of matter.
 9. Acomposition according to claim 8, wherein said support has a siliconcontent which, expressed as SiO₂, is at most equal to 1/4 of the totalweight of the composition of matter.
 10. A composition according toclaim 1, wherein at least 90%, of the ruthenium present on said supportis in the form of the said metallic phase covering said support.
 11. Acomposition according to claim 10, wherein at least 98%, of theruthenium present on said support is in the form of the said metallicphase covering said support.
 12. A process for the treatment ofcarboxylic compounds to give aldehydes or derivatives thereof,comprising the steps of subjecting the carboxylic compound tohydrogenation in the presence of a catalyst comprising a composition ofmatter as defined in claim 1.